Robert Haas <robertmh...@gmail.com> writes: > I'm interested to know whether anyone else shares my belief that > nested loops are the cause of most really bad plans. What usually > happens to me is that the planner develops some unwarranted optimism > about the number of rows likely to be generated by the outer side of > the join and decides that it's not worth sorting the inner side or > building a hash table or using an index, and that the right thing to > do is just rescan the inner node on every pass. When the outer side > returns three or four orders of magnitude more results than expected, > ka-pow!
And then there is the other half of the world, who complain because it *didn't* pick a nestloop for some query that would have run in much less time if it had. regards, tom lane -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers